<?phpclass MyexhibitionViewModel extends ViewModel{	 public $viewFields = array(        'exhibition_exhibit'=>array('exhibition_id','exhibit_id','user_id','count(distinct exhibition_id)'=>'count'),        'exhibition'=>array('id','name_cn','type_name','is_on_show','period_start','period_end','day_start','day_end','hall','logo_url','_on'=>'exhibition_exhibit.exhibition_id=exhibition.id'),    );}?>